This invention relates to manufacture of VLSI semiconductor devices, and more particularly to a method of etching for metal-gate devices.
In the manufacture of MOS VLSI devices such as 1-Megabit dynamic RAMs, for example, refractory metal gates are used, and these gates may have an overlying oxide coating needed for encapsulating the metal gate during a siliciding operation. This oxide coating presents problems, however, due to the tendancy to leave filaments of oxide at steps in the topography of the face of the silicon slice. The filaments would mask the etching of the molybdenum when the gates are patterned, thus leaving metal shorts which would cause the devices to fail.
It is the object of this invention to provide improved methods of making VLSI semiconductor devices, particularly such devices having refractory metal gates. Another object is to provide a method of VLSI manufacture which will tolerate lengthy etch steps without degrading the etch mask.